Short answer
– The most-likely author of Luke 1:26–28 (and the Gospel of Luke) is Luke the physician — a Gentile companion of the apostle Paul — as understood in standard evangelical scholarship. Evangelicals treat Luke as an historically careful, medically aware researcher who compiled eyewitness testimony and wrote an orderly account addressed to “Theophilus” (Luke 1:1–4).

Who Luke was (evangelical summary)
– Identity: Luke is called “the beloved physician” in Colossians 4:14 and is listed as a fellow worker in Paul’s letters (Philemon 24; Colossians 4:14). 2 Timothy 4:11 and the “we” sections in Acts (e.g., Acts 16:10–17; 20:5–15; 21:1–18; 27:1–28:16) point to him being a close companion of Paul.
– Background: Traditionally understood as a Gentile (Greek-speaking) and a physician; his gospel’s polished Greek and attention to detail are often cited as consistent with that background.
– Role: Not one of the Twelve and not an eyewitness of Jesus’ public ministry, but an investigator who interviewed eyewitnesses and compiled reliable testimony (see Luke 1:1–4).

Why evangelicals accept Luke as author and trustworthy
– Internal evidence: Luke himself states he carefully investigated events and compiled an orderly account from those “who from the beginning were eyewitnesses” (Luke 1:1–4). The “we” passages in Acts strongly suggest the same author of Acts traveled with Paul.
– External testimony: Early church fathers (e.g., Irenaeus, Clement of Alexandria, Tertullian) and ancient church tradition consistently attribute Luke–Acts to Luke.
– Literary and historical marks: Luke’s attention to historical detail (dates, places, named officials), coherent narrative style, and theological emphasis (salvation for Jews and Gentiles, concern for the marginalized) support the view of a careful historian, a view many evangelicals hold as compatible with divine inspiration.

Relevance for Luke 1:26–28 (the annunciation)
– Evangelical view: Luke likely drew on direct or secondhand testimony (e.g., Mary, the apostles, or early Christian witnesses) when recounting the annunciation. Luke 1:2 explains his method of using trustworthy eyewitness sources. Because Luke is seen as both diligent and close to the apostolic circle, evangelicals treat his account of the angel’s appearance to Mary as historically grounded and theologically reliable.

Typical dating
– Many conservative evangelical scholars date Luke–Acts to the 50s–60s AD (some 60s) though a range of dates into the 70s is also held. Early dating is sometimes argued on the basis of Luke’s association with Paul and lack of explicit reference to later events.

Short concluding note
– From an evangelical standpoint, Luke is the most-likely author of Luke 1:26–28: a Gentile physician and companion of Paul who carefully investigated eyewitness testimony and produced a historically credible, theologically rich account of the annunciation and the life of Jesus.