  Long-term variations are well-known in Be X-ray binaries, and are attributed
to non-orbital changes in the structure of the Be circumstellar (equatorial)
disc. However, the timescales involved are so long (tens of days, to years)
that systematic studies have been very restricted. The ~8 year MACHO monitoring
of the Large Magellanic Cloud (LMC) therefore presents an ideal opportunity to
undertake such studies of Be X-ray systems that lie within the monitored
fields. Here we present MACHO observations of two LMC Be X-ray transients, EXO
0531-66 and H 0544-665, the light curves of which show substantial (~0.5 mag)
long-term variations. However, our analysis shows little evidence for any
periodic phenomena in the light curves of either source. We find an upper limit
for detection of a short (1-100 d) periodicity in the V- and R-band light
curves of EXO 0531-66 of 0.041 mag and 0.047 mag semi-amplitude, respectively.
The upper limits for the V- and R-band data of H 0544-665 are 0.054 mag and
0.075 mag semi-amplitude, respectively. Both EXO 0531-66 and H 0544-665 become
redder as they brighten, possibly due to variations in the structure of the
equatorial disc around the Be star. Spectra of both sources show H$\alpha$
emission; for EXO 0531-66 we find the emission varies over time, thereby
confirming its optical identification.
