The wideband microstrip antenna is realized by employing multiple resonant modes in the antenna cavity in the form of parasitic patches or the resonant slots cut inside the patch. Instead of this, in the isosceles triangular microstrip antenna, which is a variation of equilateral triangular microstrip antenna, wider bandwidth is achieved by changing the isosceles angle that alters the spacing between patch TM10 and TM11 resonant modes. This paper presents the design of proximity fed 110° Isosceles triangular microstrip antenna using the Bow-tie shape of the ground plane. The isosceles angle yields optimum separation between TM11 and TM10 mode frequencies and Bow-tie shape ground plane achieves the impedance matching at the two resonant modes on a reduced substrate thickness to yield reflection coefficient bandwidth of 870 MHz (58.5%). Against the rectangular ground plane profile, use of Bow-tie shape of the ground plane achieves reduction in substrate thickness by 0.02λc (0.02λ10) with nearly 4% increment in the reflection coefficient bandwidth. The reduced ground plane design realizes peak broadside gain of nearly 7 dBi, which is nearly the same as that obtained using conventional rectangular ground plane design. Thus, proposed design provides the wideband solution without using additional patches and resonant slots but on a reduced substrate thickness. With the obtained antenna characteristics, equivalent of the proposed design can find applications in various wireless communication systems like, GSM, LTE band applications.