  Gravitational lenses can magnify distant galaxies, allowing us to discover
and characterize the stellar populations of intrinsically faint, quiescent
galaxies that are otherwise extremely difficult to directly observe at high
redshift from ground-based telescopes. Here, we present the spectral analysis
of two lensed, quiescent galaxies at $z\gtrsim 1$ discovered by the ASTRO 3D
Galaxy Evolution with Lenses survey: AGEL1323 ($M_*\sim 10^{11.1}M_{\odot}$,
$z=1.016$, $\mu \sim 14.6$) and AGEL0014 ($M_*\sim 10^{11.5}M_{\odot}$,
$z=1.374$, $\mu \sim 4.3$). We measured the age, [Fe/H], and [Mg/Fe] of the two
lensed galaxies using deep, rest-frame-optical spectra (S/N $\gtrsim
40$~$\mathring {\mathrm A}$$^{-1}$) obtained on the Keck~I telescope. The ages
of AGEL1323 and AGEL0014 are $5.6^{+0.8}_{-0.8}$~Gyr and
$3.1^{+0.8}_{-0.3}$~Gyr, respectively, indicating that most of the stars in the
galaxies were formed less than 2~Gyr after the Big Bang. Compared to nearby
quiescent galaxies of similar masses, the lensed galaxies have lower [Fe/H] and
[Mg/H]. Surprisingly, the two galaxies have comparable [Mg/Fe] to similar-mass
galaxies at lower redshifts, despite their old ages. Using a simple analytic
chemical evolution model connecting the instantaneously recycled element Mg
with the mass-loading factors of outflows averaged over the entire star
formation history, we found that the lensed galaxies may have experienced
enhanced outflows during their star formation compared to lower-redshift
galaxies, which may explain why they quenched early.
