Texas! Sage by Sandra Brown was published in 1991.
Sandra Brown - Texas! Sage book description:
The youngest heir to her family’s oil fortune, Sage has always been the unbridled spitfire in the Tyler clan. Now, fresh out of the University of Texas with her MBA in hand, she’s looking to settle down at last with her safe, predictable upper-crust fiancé. But unbeknownst to Sage, her well-ordered future is about to be suddenly and irrevocably upended.
Into her life saunters Harlan Boyd, an irritating, rootless drifter recently hired by her brothers for a Tyler Drilling Company project. Harlan’s just the sort of man Sage should avoid — particularly during this rare period of vulnerability. But there’s something irresistible about the laconic cowboy that intrigues her, makes her want to reveal all her secrets to him, and even forces her to reconsider the path her life will take. But can she trust a man who shares her maverick spirit — and harbors long-held secrets of his own?
When a financial crisis threatens to wreck Tyler Drilling for good, Sage and Harlan must channel their simmering chemistry into the immediate task of saving the family business. Working side by side in close quarters, Sage will discover that a man who seems all wrong for her may prove to be the right choice after all.
Crackling with the lightning heat of a Lone Star summer, Texas! Sage is a fitting final chapter for the Tyler family saga.