The best thing about reformed theology is that it recognizes that God has one plan and one purpose across redemptive-history and that covenant is the formal and material means of establishing the unity of redemptive-history. I believe in covenant theology, I think what we call a covenant of grace is God’s plan for taking people from being “in Adam” to being “in Christ.” But I reject the binary covenant of works vs. covenant of grace view, also called bi-covenantalism. So I’d breakdown covenant theology this way:
First, there is no covenant of works which required Adam to keep a law that was a protological version of the Mosaic law and covenant.
The Adamic adminstration was a probationary period rather than a meritorious exercise. Adam could have retained his relationship with God and even gained immortality had he remained obedient to God in the garden during that probationary period in Eden. Adam’s failure was not the failure to keep the commandment as a law, which, if obeyed, would have acquired merit for himself; rather, breaking the commandment meant severing his relationship with God on account of his desire for autonomy from God. Salvation will henceforth mean restoring the ruined relationship between Creator and humanity as opposed to accruing the meritorious law-keeping that Adam allegedly failed to achieve.
Following on from that, the Mosaic covenant was not a republication of an Adamic covenant. The Mosaic covenant was a temporary, national, and preparatory covenant within the over-arching covenant of grace. The role of the Mosaic covenant was to: (1) temporarily cocoon God’s saving purposes within Israel to ensure their preservation; (2) to protract Israel’s capacity to worship God by insulating them from the Canaanite nations; (3) to use Israel to project God’s first order purposes into the world; (4) to demonstrate the consequences of sin; and (5) to designate Israel as the means for the revelation of the Messiah. In other words, the Mosaic covenant, with its various curses and blessings, was like a time-capsule or life-boat, to preserve God’s saving promises until the time for their revelation in the coming of the Son.
Second, I posit a covenant of grace as the sub-structure within God’s plan to bring salvation through Jesus Christ and so unite humanity to himself in the new creation.
The covenant of grace may be conceptually correlated with the “eternal covenant” mentioned in Heb 13:20. This eternal covenant included the sacrificial “blood” of Jesus, which is an expression of God’s plan for Jesus to be the Lamb of God slain before the creation of the world (Rev 13:8). This eternal covenant delivers people from the sins committed under the “first covenant” (i.e., Sinaitic covenant) according to the author of Hebrews and Paul (Heb 9:15; Gal 3:13), and also those outside the parameters of Israel who have been brought near to God, received peace, and now know the promise and hope of the “covenants” (Eph 2:12-14). Hence, the covenant of grace is the overarching conceptual reality behind the Abrahamic covenant, Mosaic covenant, and the new covenant that avails for the redemption of God’s people. The covenant of grace is God’s rescue plan to turn the corrupted garden of Eden into the garden city of a new Jerusalem.
The covenant of grace means that God has one plan for salvation. The “eternal gospel” (Rev 14:6) was first announced in the promise given to Eve about her off-spring crushing the serpent’s head (Gen 3:15), it was revealed in advance to Abraham (Gen 15:5; Gal 3:18), the gospel of grace was disclosed during the period of the law (Ps 51:1-19; Isa 52:7; Hab 2:4), it culminated in the message of Jesus (Mk 1:14-15), and the apostolic proclamation of Jesus (e.g., Acts 5:42; 8:12; 10:36; Rom 1:3-4; 1 Cor 15:1-5; 1 Pet 1:12). This is why the Heidelberg catechism says: “[T]he holy gospel, which God Himself first revealed in Paradise. Later, He had it proclaimed by the patriarchs and prophets, and foreshadowed by the sacrifices and other ceremonies of the law. Finally, He had it fulfilled through His only Son” and the Scots confession speaks similarly, “This promise was repeated and made clearer from time to time; it was embraced with joy, and most constantly received by all the faithful from Adam to Noah, from Noah to Abraham, from Abraham to David, and so onwards to the incarnation of Christ Jesus.”
The covenant of grace, properly understood, allows us to correlate not confuse “law” and “gospel.” The differences between “law” and “gospel” is one of contrast, not conflict since across the covenant of grace every redemptive-historical moment features elements of salvific gift and divine demand. The Mosaic law is antithetical to gospel only when the law is regarded as a means of salvation and a moat around the saved to keep out the unsaved. The Mosaic legislation spelled out the personal and national obligations of Israel for temporal blessings under the covenant of grace (see Lev 18:5; Deut 30:16). The law was never intended as a ladder to God nor the basis for salvation. The law was given to a redeemed people, not to redeem the people, and it was given to point the people to the redemption still to come. The law and prophets witness to the gospel (Rom 3:21), the law was our guardian to lead us to Christ (Gal 3:24), Jesus came not to abolish the law but to fullfil it (Matt 5:17; Luke 16:17) and Christian faith upholds the law even though Christians are not strictly under its jurisdiction (Rom 3:31; 6:14-15; Gal 5:18). In effect, with Christ, the law ends as the primary way of defining the identity of God’s people and spelling out their moral obligations (see Matt 11:13; Luke 16:16; Rom 10:4; Heb 7:11-12). The law is fulfilled, not in the sense of being nullified or castigated, but is recast in a new mode of expression distilled into the love command and appropriated for the multi-ethnic church (see Matt 5:43; Gal 5:6, 14; Rom 13:9-10; Jas 2:8). Clearly there are and discontinuities and continuities in God’s demands for his people across the covenants: (1) In terms of discontinuity, the law no longer provides an ethnic insularity nor a prescribed pattern of conduct for God’s people, they are under grace not law, thus the obligations of the new covenant are not the moral law of the Decalogue, but the Levitical love command as the summation of the law, the teaching of Jesus, the example of Jesus, and life in the Spirit, those things represented as the “law of Christ” (Gal 6:2; 1 Cor 9:21); (2) In terms of continuity, every phrase of redemptive-history conveys an indicative (God for us) and imperative (God commands us). The indicatives include God’s common grace to Adam, God’s call of Abram out of idolatry, God’s deliverance of the Hebrews from Egypt and the Jews from Babylon, and the death and resurrection of Jesus. The imperatives include the divine commands given to Adam, Abram’s summons to obey, the Mosaic legislation, heeding the prophetic word, and the teachings/example of Jesus. Viewed this way, law and gospel are not diametrically opposed foes, but a feature of every epoch of redemptive-history.
The covenant of grace, worked out accordingly, means that we cannot can play off the Abrahamic covenant against the Mosaic covenant, as if one is an expression of grace and another an expression of the law. I would go so far as to say that the Abrahamic promises are telescoped into the Mosaic covenant. In fact, the promises in Gen 12:1–3 are virtually restated in Exod 19:4–5, so that the Mosaic covenant is an expression of the Abrahamic promises cocooned around the elect people. On this point Gerhardus Vos rightly noted:
The Sinaitic covenant is not a new covenant as concerns the essence of the matter, but the old covenant of grace established with Abraham in somewhat changed form. The thesis that it must be a new covenant is usually derived from the fact that Paul so strongly accents the law over and against the promises as different from them (e.g., Gal 3:17ff). But thereby one thing is forgotten. Paul nowhere sets the Sinaitic covenant in its entirety over against the Abrahamic covenant but always the law insofar as it came to function in the Sinaitic covenant.
 Theodoret of Cyrus, Questions of the Octoteuch 1, “Adam was set a trial with regard to the [tree of knowledge of good and evil], whereas the tree of life was proposed as his prize for keeping the commandments” cited in Frances M. Young, Construing the Cross: Type, Sign, Symbol, Word, Action (London: SPCK, 2016), 50.
 Heidelberg Catechism, Q. 19.
 Scots Confession, § 4.
 William J. Dumbrell, Covenant and Creation (Nashville: Nelson, 1984), 89–90.
 Gerhardus Vos, Reformed Dogmatics (4 vols.; Bellingham, WA: Lexham, 2012-14), 2:128-29.